1. Field of the Invention
The present invention relates to an ink-jet head that ejects ink onto a recording medium to conduct recordings, and also to a method for manufacturing the ink-jet head.
2. Description of Related Art
An ink-jet head used in an ink-jet recording apparatus such as ink-jet printers has a passage unit provided with many pressure chambers and many nozzles communicating with the pressure chambers. Ink is distributed from an ink tank to the pressure chambers, and pressure is selectively applied to each pressure chamber, so that the volume of each pressure chamber is changed and ink is ejected through a corresponding nozzle. In order to apply pressure to the respective pressure chambers, an actuator is disposed on a face of the passage unit that has the pressure chambers formed thereon.
In general, the passage unit and the actuator are adhered to each other through the steps of: forming an adhesive layer on wall portions defining the pressure chambers in the passage unit; positioning the actuator onto the passage unit; disposing a pressurizing member such as a heater on the actuator; and then performing pressure application and heating. When a thickness of the adhesive layer between the passage unit and the actuator is nonuniform, there may arise a problem that the pressure chambers vary from each other in pressure generated therein and therefore the nozzles exhibit different ink ejection characteristics from each other to result in deterioration in image quality. In an extreme case, an ink leakage between the pressure chambers can be caused. Accordingly, for a prevention of a variation in ink ejection characteristics, it has been desired that the adhesive layer has a uniform thickness.
A piezoelectric element is typically adopted as the actuator. In this case, an electrode as a surface electrode is formed on the piezoelectric element and a drive signal is outputted to the surface electrode, to thereby deform the piezoelectric element and accordingly change the volume of the pressure chamber. In this technique, sometimes, a surface electrode is formed individually for each pressure chamber, and each surface electrode includes a main body having a slightly smaller area than a pressure chamber area and an extension extending to an outside of the pressure chamber area, i.e., extending to a position opposing a wall portion that defines the pressure chamber (see Japanese Patent Laid-open No. 11-34323). In this construction, a contact between the surface electrode and another member such as a flexible flat cable is formed on the extension of the surface electrode. An electrical connection between the surface electrode and the cable is achieved by soldering the cable to the contact or pressing against the contact a contact member such as a terminal.
In the above-described construction, however, the contact with the cable is formed on the extension of the surface electrode. Consequently, when the cable is disposed on the piezoelectric element, there is formed only a relatively narrow space between the cable and the piezoelectric element. When, under such a condition, the cable is soldered onto the extension of each surface electrode, overflow of a solder tends to cause a short circuit between neighboring surface electrodes. This problem becomes prominent particularly when the pressure chambers are densely arranged in the passage unit.